The present invention relates to data processing systems, and more particularly, to a data processing system having optically linked subsystems.
Optical keyboards are known in the art. For example, in U.S. Pat. No. 3,856,127, issued to Uri Halfon et al., there is shown a photoelectric keyboard having light sources and associated light-sensitive photocells arranged in an X-Y matrix. Shutters are selectively operable to intercept light passing from each source to its associated photocell. The interception of the light indicates that a key associated with the shutter has been moved or depressed. In U.S. Pat. No. 3,614,402, issued to Leonard James Higgins, there is shown an optical keyboard device having a light source and a light detector, with each key on the keyboard associated with an individually coded target member. The coded target members selectively pass, reflect or absorb, in a particular coded fashion, light passing from the source to the detector so that the depression of each key results in a unique coded light pattern. In U.S. Pat. No. 3,860,754, issued to Roger L. Johnson et al., there is shown a light beam X-Y position encoder for detecting the position of an obstacle, such as a finger, on a display surface. There are included light sources and light detectors arranged along X and Y axes of the display surface, with the light sources sequentially strobed.
It is now widely believed that in future data processing systems, there will be extensive use of optical transmission lines to interconnect subsystems within the data processing systems. Optical transmission lines overcome many problems commonly encountered in the transmission of data in data processing systems, such as interference resulting from EMI (electromagnetic interference), RFI (radiofrequency interference), and ground loop problems. Although optical keyboards have been proposed in the past, there is not known any method whereby an optical keyboard may be linked directly to an optical transmission line connecting the keyboard to some other subsystem in a data processing system. Rather, optical keyboards have used optical signals to merely detect the depression or movement of a key on a keyboard, with the optical signal converted into an electrical signal within the keyboard subsystem prior to being transmitted elsewhere in the system.